Method, an apparatus and a knife for mechanical releasing of ribs in a part carcass

ABSTRACT

The apparatus comprises a knife ( 21 ) with a substantially rectilinear cutting edge ( 27 ) and mounted in a knife holder ( 23, 24 ), a device with a holder for suspending the part carcass by the spine, and means ( 1, 4, 5 ) for establishing a relative movement between the part carcass ( 2 ) and the knife ( 21 ) in a direction in parallel with the spine ( 9 ), the knife holder ( 23, 24 ) being adapted to displace the knife ( 21 ) in a plane perpendicular to the direction of the spine and preferably to turn the knife about an axis in parallel with the cutting edge ( 27 ).

The present invention relates to a method for mechanical releasing ofthe ribs and the meat positioned therebetween from the adjacent meat ina part carcass with spine and split along the central longitudinalplane.

The invention thus relates in particular, but not exclusively, toreleasing of the riblet, i.e. the ribs with the adherent meat andpossible sternum, in a fore-end of a splitted carcass, in particular pigcarcass, divided in two or three, but may also be used in connectionwith a middle or a loin.

DK-B-172 327 (Slagteriernes Forskningsinstitut) discloses a method fordeboning a fore-end of a pig carcass. It is said that the riblet may becut from the fore-end by means of a knife (not shown or described indetail) which is mounted on a tool which is moreover used for freeingthe neck bone. The knife is to be moved along and guided by theunderside of the ribs, and the movement has to be oblique relative tothe longitudinal direction of the neck bone and is to take place in adirection away from the neck joint and the neck bone. It is further saidthat the cut has to be made in a direction away from the neck jointtowards the distal end of the neck bone, i.e. from in front.

EP-A-0 502 581 discloses a method for mechanial releasing of ribs in apart carcass, in which the spine is cut free first by means of acircular saw, whereafter the ribs are cut free one by one by means of aspecial loop-like knife which is passed along each single rib, the meatpositioned between the ribs being left connected with the part carcass.

WO-A-99/08538 (Slagteriernes Forskningsinstitut) discloses an apparatusfor mechanical removal of the spine from a part of a carcass, inparticular a fore-end of a splitted pig carcass. The apparatus comprisesa conveyor with a band supporting and advancing the fore-end, and aguide rail towards which the spine of the fore-end is pressed such thatthe spine is kept substantially rectilinearly extended. The spine is cutfree from the fore-end by means of knives which are positionedstationarily along the guide rail.

The object of the invention is to provide a method, an apparatus and aknife for mechanical releasing of the ribs and the meat positionedtherebetween from the adjacent meat of a part carcass of a splittedcarcass with spine, said method, apparatus and knife being toleranttowards the varying anatomic conditions of the part carcasses, such thatthe release may take place without the part carcasses having to bemeasured and such that the release may be equally satisfactorilyperformed irrespective of whether it is a question of a big or a smallpart carcass. The method is preferably to be used in connection withsaid apparatus.

This object is met according to the invention by means of a method whichis characteristic in that the part of the spine carrying the ribs isbrought into engagement with a holder, that the thus secured partcarcass and a knife with a substantially rectilinear cutting edge endingin a point is moved towards each other so that the point of the knife isinserted from behind at the exterior side of the rib head of therearmost rib and the cutting edge is brought to abut on a rib surface,and that the secured part carcass and the knife is moved further towardseach other in the direction of the spine while the knife is kept, seenalong the cutting edge in the direction of the point, in a predeterminedangular position obliquely inwards and upwards relative to the carcass,its central plane and a second plane which is perpendicular to thecentral plane and in parallel with the spine and the knife is movedalong the ribs away from the spine.

It has surprisingly turned out that this method makes it possible to usea knife with a rectilinear cutting edge which by a suitable choice ofangular position will follow all the ribs in the part carcass ratherclosely such that a comparatively simple, but effective method isobtained for mechanical releasing of ribs, which method is independentof anatomic differences from carcass to carcass and the variations inthe position of division at the cutting.

The method has proved particularly suitable for removal of riblets, asit utilizes the fact that there is no big variation from carcass tocarcass at the spine, whereas there may be a big variation in respect ofthe positioning of the sternum. The method is not very sensitive to saidvariation.

When introduced from behind, the knife may be positioned between thestationary knives in said apparatus, ahead of a knife or a saw cuttingoff the ribs. By thus using said apparatus, it becomes possible toestablish the positioning of the rib head of the rearmost rib and thusthe insertion position sufficiently well so that the cutting may bestarted without any detailed knowledge of the size etc. of the partcarcass.

Preferably the point of the knife is at least during the first phase ofthe releasing moved substantially rectilinearly forwards relative to thepart carcass.

The position of the foremost rib in the part carcass relative to theknife is preferably detected, and the movement of the knife along theribs away from the spine and the possible rotation of the knife aroundan axis parallel with the edge, depending on the movement of the knifeand the part carcass towards one another in the direction of the spine,is controlled on basis of said detection.

If the part carcass comprises a sternum, which is the case with afore-end, the method preferably comprises the steps that the knife, whenthe knife has been advanced a distance along the ribs away from thespine, is rotated about an axis which is substantially parallel to thecutting edge into a smaller angle of attack with the the ribs, that theknife during continued movement towards the part carcass in thedirection of the spine is moved further away from the spine obliquelytowards the central plane of the carcass, and that the breast side, whenthe knife has thus been advanced yet another predetermined distance ispressed downwards and towards the carcass, following which the knifeunder a continuous movement relative to the part carcass in thedirection of the spine is taken sideways out from the part carcass. Inthis manner the knife may advance along and be guided by the ribs, untilit is supposed to meet the gristle positioned in continuation of theribs in case of a relatively small animal, whereafter the breast side islifted by rotating the knife into a smaller angle of attack to preventthe knife from cutting into the gristle and then later into the sternum.When the knife is advanced so far that it is expected to reached aposition below the sternum at the foremost rib, even in case of arelatively big animal, the breast side is pressed downwards and towardsthe carcass to ensure that the further incision is made so close to thesternum as possible.

The angle of the cutting edge relative to the centre plane is 15°-30°,preferably 20°-26°, and further preferably approx. 23° at least at theinsertion of the knife and when the knife passes a possible sternum, andthat the angle relative to the second plane is 5°-20°, preferably 7°-17°and further preferably approx. 11° at least at the insertion of theknife. Within these limits it is possible depending on the actual raceof the slaughtered animals, to find angles, at which it is possible tohold the cutting edge in a constant angle relative to the centre planeand the second plane. This entails that a relative simple apparatus maybe used for holding and guiding the knife.

The knife is preferably pressed sideways towards the ribs while movedalong them and is held in a cutting angle adjusted such that the flankof the knife abuts the ribs. Hereby is obtained that the rib, whichprotrudes relative to a cylinder or conus surface which the cutting edgedescribes during its movement, is pressed into such a surface in such amanner that the cutting edge slides across all the ribs and frees asmuch as possible of the adjacent meat. The rearmost rib in a partcarcass has normally a substantially bigger curvature than the foremostrib. By using said obliquely extending blade problems in respect ofdiffering cutting angles at the foremost and the rearmost ribs areavoided, the knife not starting to cut at the foremost rib until it hasmade an incision along a substantial curved portion at the rearmost riband thus has reached a portion extending substantially in the same wayas the first part of the foremost rib. The flank thus substantiallyabuts on all the ribs, which gives a tight and correct cut along thesurfaces of the bones. During the cutting the knife turns all the time,its flank abutting optimally on the bone surfaces.

At the beginning the knife is preferably inserted at a predeterminedpoint relative to the holder and next to the rearmost rib at a distancetherefrom, and is due to the insertion brought into abutment on thisrib. Hereby a higher tolerance in respect of the insertion of the knifeis obtained.

The knife is preferably rotated about an axis containing the cuttingedge. In this manner the knife angle relative to the ribs is adjustedwithout influencing the arrangements pressing the knife towards the bonesurfaces.

The object is further met by means of an apparatus for use in mechanicalreleasing of the ribs and the meat positioned therebetween from theadjacent meat of a part carcass of a splitted carcass with a spine,which apparatus is characteristic in comprising a knife having asubstantially rectilinear cutting edge ending in a point and beingmounted in a knife holder, a device with a holder which can be broughtinto engagement with the part of the spine of the part carcass carryingthe ribs, and means for establishing a relative movement between thepart carcass and the knife towards each other in the direction of thespine and further to move the knife away from the spine.

The knife holder is preferably adapted to hold the knife with thecutting edge, viewed along the cutting edge in the direction of thepoint, at a predetermined angle which, when the spine of a part carcassis in engagement with the holder, is obliquely inwards and upwardsrelative to the carcass, its central plane and a second plane which isperpendicular to the central plane and parallel with the spine.

The knife holder is preferably adapted to displace the knife in a planesubstantially perpendicular to the direction of the spine and preferablyto rotate the knife about an axis which is parallel to the cutting edge.

The apparatus preferably comprises a detecting device for detecting thepassage of the foremost rib of a part carcass by a relative movementbetween a secured part carcass and the knife towards one another in thedirection of the spine, and guiding means for guiding the displacementof the knife away from the spine and the possible rotation around anaxis parallel with the edge, depending on the movement of the knife andthe part carcass towards one another in the direction of the spine onbasis of the detection. In this way, a correct guiding of the movementof the knife is obtained irrespective of whether the part carcass hasbecome somewhat longer or shorter during the cutting of the carcass.

Moreover, shackles are preferably provided for guiding the breast sideof the part carcass. In this way, a correct cut is secured in the areaaround the sternum.

The object is further met by an asymmetric knife for use for mechanicalcutting free of the ribs and the meat positioned therebetween from theadjacent meat in a part carcass of a splitted carcass with spine, whichknife is characteristic by an elongate, rigid blade with a substantiallyrectilinear cutting edge ending in a point, a bias cutoff of the bladeextending from the point, two substantially parallel side surfaces and aflank angled relative to the adjacent side surface, said flank extendingfrom the cutting edge to a line positioned approx. 4-25 mm, preferablyapprox. 5-20 mm, further preferably approx. 7-15 mm and for instanceapprox. 10 mm from the cutting edge, the angle (α) between the flank andthe adjacent side surface being smaller than 180°, preferably smallerthan 175° and for instance approx. 170°.

Ribs are curved, but are not identical from animal to animal even withinthe same race. The knife according to the invention is suited forsliding over the ribs and thereby be guided in a predetermined path, asthe knife on account of the relatively narrow flank is little sensitivein respect of its guiding along the ribs relative to its precise angularposition in relation to the surface of the ribs, a given rotation of theknife blade around an axis parallel with the cutting edge only meaninglittle to the distance of the cutting edge from the surface of the ribs.At the same time the width of the flank is sufficient for ensuring thatthe knife blade may slide across a possible hollow in a rib without thecutting edge penetrating into the hollow and into the bone. On accountof the angle between the flank and the adjacent side surface it ispossible, without influencing the dimensions of the flank, to design theknife blade with sufficient thickness and width to ensure the requiredrigidity which is a prerequisite for pressing the rib into a cylinder orconus surface.

The flank may be plane or convex to correspond to the curvature of theribs or it may be slightly concave.

The point of the knife is bent out of the plane of the blade oppositethe side of the flank and in that preferably a bevelling is providedbetween the flank and the cutting edge. This prevents the point fromhitting a rib which might be positioned particularly far outside thecylinder or conus surface described by the cutting edge, and by means ofthe bevelling, increased safety is obtained against the knife hitting arib if the predetermined angle of the knife is a little too steeprelative to a certain animal or in case of protrusions on a rib.

In the present description is said that the knife is inserted into themeat or that knife and part carcass is moved towards each other. By thisshould be understood that the meat may be moved relative to a knifestationary in the direction of the spine, that the knife is moved intothe meat in the direction of the spine, or that both meat and knife maybe moved (but move mutually) in the direction of the spine. When said inthe present description that the meat is moved towards a knife, thisshould also include the embodiment in which the meat is stationary andthe knife is guided in the meat.

The invention will be described in detail in the following by means ofan example of an embodiment with reference to the schematic drawing, inwhich

FIG. 1 shows an apparatus for removal of the spine from a fore-end, inwhich apparatus the invention is incorporated,

FIG. 1a a guide mechanism,

FIG. 2 a view from the side of a knife according to the invention,

FIG. 3 a sectional view along the line III—III in FIG. 2,

FIG. 4 the knife in FIG. 2 seen in the direction of the arrow IV,

FIG. 5 the rearmost rib during a first phase of the releasing of theribs,

FIG. 6 a view corresponding to FIG. 5 during a later step of thereleasing of the ribs,

FIG. 7 a view corresponding to FIG. 5 during the final step of thereleasing of the ribs, and

FIG. 8 curves schematically illustrating the movement of the knife.

The apparatus shown in FIG. 1 for removal of the spine from a fore-end 2with a shank 2 a comprises a conveyor belt 1 with a conveying direction(arrows 31), the purpose of which is to support and advance the fore-end2. In FIG. 1 the spine 9 of the fore-end is hatched.

Above the conveyor belt 1 a guide rail 3 extends, said rail serving asfixed abutment for the spine 9 of the fore-end 2. The conveyor belt 1 isspring suspended and presses the fore-end 2 up against the guide rail 3.Substantially perpendicular to the abutment surface of the guide rail 3a side guide is provided in the form of a driven continuous chain 4 withcontact plates 5 provided with spikes. A vertical band conveyor guides 6the fore-end 2 towards this chain 4 and presses the vertebras of thespine 9 into the spikes on the contact plates 5. The band conveyor 6 isspring-suspended in order to be adjustable to the fore-end 2. In the farend the band conveyor 6 passes into pressure rollers 7 which are alsospring-suspended. The apparatus in FIG. 1 has a first knife tool 8 forseparating the meat of the fore-end 2 from spinous processes 12 and thedorsal side of the spine 9. In front of the tool 8 a presser shoearrangement with a contact plate 14 is provided, said arrangementserving during the cutting of the tool 18 in particular for pressingdown the meat opposite the first cervical vertebrae.

Immediately behind the knife tool 8 a resiliently mounted guide disc 17is provided which assumes a position in the track left by the cuttingtool 8. The guide disc 7 supports the spinous processes 12 and pressesthe spine 9 firmly against the contact plates 5 of the chain 4 and theguide rail 3. Behind the guide disc 17 a second cutting tool 18 with aknife blade 19 is provided. The second cutting tool 18 is adapted to cutthe ribs 10 a, 10 b at the rib heads 13 and to separate the meat fromthe lateral side of the spine 9 (see FIG. 5). The part of the cuttingtool 18 cutting the ribs is preferably a circular saw (not shown) whichis placed upstream of the knife blade 19.

In addition to the guide disc 17 a third tool 20 is provided which hastwo knives perpendicular to each other and which serves to cut the neckbone strip free from the underside and the transverse processes of thecervical vertebrae without cutting the strip's connection with the neckfillet.

The chain 4 with the contact plates 5 and the guide rail 3 cooperatewith the guide disc 17 as a holder for the spine 9.

For further details in the apparatus shown in FIG. 1 and described untilnow, reference is made to WO-A-99/08538.

Moreover, the apparatus shown in FIG. 1 is provided with a knife 21according to the present invention. The knife 21 has a point 22 and isat the end, which is opposite relative to the point, mounted on aturning plate 23 which in turn is mounted on a transport mechanism 24 ofthe kind shown in FIG. 1a. The mecahnism 24 moves the knife in a planewhich is substantially perpendicular to the longitudinal direction ofthe spine and presses it during the first phase of the cutting towardsthe ribs with such a force that they yield partially in the rib heads.The transport mechanism 24 comprises a column 35, which on a sledge 36can be moved vertically, as shown by a double arrow, by means of a motor37. A cross beam 38 is mounted on the sledge 36 and can be moved inhorizontal direction as shown by another double arrow, such that theturning plate 23 which is mounted at the end of the cross beam 38 can bemoved vertically and horizontally in a plane by means of the guidingmechanism 24. It should be noted that the turning plate 23 is mountedobliquely relative to this plane. The knife 21 can by the turning of theturning plate 23 be turned about its cutting edge, and the knife 21 andthe turning plate 23 can by means of the guiding mechanism 24 be movedin a plane perpendicular to the guide rail 3. In the embodiment shownthe knife 21 is held with its longitudinal axis in a predetermineddirection. The knife blade 25 is thus preferably held such that an angleβ of 5°-20°, preferably 7°-17°, and in the example approx. 11° relativeto the transport direction, seen in the plane of the conveyor belt 1,and an angle of 15°-30°, preferably 20°-26°, and in the example approx.23° in relation to the direction of transport as viewed in a planeperpendicular to the plane of the conveyor belt 1, the knife blade 25from the turning plate 23 extending obliquely up towards the viewer inFIG. 1.

The blade 25 of the knife 21 is shown in detail in FIGS. 2-4 and has acomparatively big thickness, for instance approx. 6 mm. The knife blade25 has in the example a plane flank 26 which has a sufficient width toensure a good, sliding abutment on the ribs. The width of the flank isapprox. 4-25 mm, preferably approx. 65-20 mm, further preferably approx.7-15 mm and for example approx. 10 mm. Between the flank 26 and thecutting edge 27 of the knife 27 a small bevelling 28 is provided which,as will be explained in detail in the following, is to prevent thecutting edge from cutting the ribs. There is between the flank 26 andthe adjacent side surface 30 an angle a of approx. 170°. The knife blade25 has a comparatively wide face 29 on account of the asymmetry of theknife blade 25. As will be seen from FIG. 4 the end of the knife blade25 is bent slightly downwards at the point 22.

Above the conveyor belt 1, a detecting device 37 is provided fordetecting the surface of the fore-end 2 and in particular for detectingand giving a signal when the foremost rib 10 b passes. Furthermore, anarm 38 is provided which carries a first shackle 39 extending in curvedownwards towards and along with the conveyor belt 1, and a secondshackle 40 extending in a curve towards and along the spine of a passingfore-end to guide said fore-end. The functioning of the shackles 39, 40will be explained in detail in below.

By means of the equipment described hitherto, the method according tothe invention may be carried out as follows.

The fore-end 2 is by means of the conveyors 1 and 6 brought intoengagement such that it is retained at its spine 9 by the chain 4 withcontact plates 5 and the guide rail 3. It is thus fixed or secured in aplane perpendicular to its longitudinal axis, but can be moved forcedlyin its longitudinal direction. The knife 8 cuts along the spinousprocesses 12 and the spine, when the spine by force is advanced towardsthe knife 8. The succeeding knife 21 is held with its blade 25 in apredetermined position, and when the fore-end 2 is advanced towards itas shown by arrows 31 the point 22 of the knife will penetrate into thefore-end 2 at the point 32 (FIG. 5) next to the rib head 13 of therearmost rib 10 a. The advancing of the fore-end 2 continues so that theknife gets in contact with the rib 10 a on account of the obliqueposition of the blade and starts cutting along the rib 10 a.

During the movement of the fore-end 2, it slides under the detectingdevice 37 which detects the passage of the foremost rib 10 b and gives asignal to the control device which controls the guiding mechanism 24 andthe turning plate 23 for the knife 21 depending on the position measuredand the travelling speed of the fore-end in the direction of the spine.

The movement of the knife is shown schematically by the curves in FIG. 8which show the positioning of the knife point 22 in a given cross-plane,y being the transport direction 31 of the fore-end 2 and z beingvertically upwards positively towards the viewer, whereas x isperpendicular to y and z and positive towards the left of the FIGS. 1and 5-7. Rot indicates the rotation angle of the knife blade 25, 0 isfacing the conveyor belt 1 broadsidedly and the cutting-edge is to theleft of FIGS. 1 and 5-7, and positive values indicate that the blade isturned towards an edge position in which the cutting-edge is closer tothe conveyor belt 1.

On account of the predetermined angular position of the knife blade 25and the rotation of the turning plate 23 and the movement of the knife21 towards the left, the attacking point of the cutting edge 27 oppositethe rearmost rib 10 a during the relative movement between the fore-end2 and the knife 21 moves from the point 32 to the point 34 via a path 35substantially as shown. The blade performs a turning during the cuttingat the ribs. The point 22 being bent slightly downwards and theintroduction taking place in a fixed safe distance from the rib head 13,it is with great certainty avoided that it hits a rib during thisinitial step.

The flank 26 is in abutment on the ribs, and the knife blade 25 will notcut into the ribs 10 a, 10 b. As the knife is rigid and the ribsresilient at their rib heads and as the knife is guided sideways andvertically in accordance with the guiding curve which establishes apressure between knife and fore-end, the ribs will be forced to followthe line defined by the knife, such that a cut close to the ribs isperformed irrespective of anatomic differences between the partcarcasses. The oblique position in question also contributes to this.

Simultaneously with the continuous advancing of the fore-end, thelateral and vertical movement and the rotation of the knife 21 on theturning plate 23 is continued such that the blade 25 in abutment on theribs follows a curve forwards to a predetermined position slightlybehind the position shown in FIG. 6, and in which the cutting edge 27 isexpected not yet to have arrived to the gristle connections 36 betweenthe ribs and the sternum. At this time the angle of attack of the bladeis small so that the part of the fore-end 2 comprising the sternum 11 israther lifted by the side of the blade 25 as shown in FIG. 6, and theknife blade 25 is kept rotated so that the flank extends substantiallyin parallel to the ribs until the predetermined positions shown in FIG.7, in which the cutting edge 27 is expected to be below the sternum 11.At this time the part of the fore-end 2 comprising the sternum islowered again, the shank 2 a passing under the first shackle 39 whichpresses it down, and simultaneously the second shackle 40 gets intoabutment on the skin of the fore-end 32 close to the sternum 11 suchthat this part of the fore-end is brought to assume a more well-definedposition relative to the movement and rotation of the knife. At thesternum 11, the knife is turned more and more upwards such that theknife during the further movement of the fore-end 2 cuts closely to thesternum which is thereby cut free of the fore-end 2. The second shackle40 thus has the function of keeping the sternum 11 in a predeterminedposition, which contributes to making the knife blade 25 cut at thedesired point in the fore-end 2 at the sternum. Without the secondshackle 40, the position of the sternum would be indistinct, parlybecause the size of the various fore-ends is difffering, partly becausethe sternum on account of the resiliency of the meat may move. Theriblet is now cut free.

When the fore-end subsequently passes the second cutting tool 18, theriblet is separated completely from the fore-end 2, the circular saw ofthe cutting tool cutting through the rib heads connecting the ribs withthe spine.

What is claimed is:
 1. A method for mechanical releasing of the ribs andthe meat positioned therebetween from the adjacent meat in a partcarcass of a splitted carcass with spine, characterized in that the partof the spine (9) carrying the ribs is brought into engagement with aholder (3, 4, 5, 17), that the thus secured part carcass and a knife(21) with a substantially rectilinear cutting edge (27) ending in apoint (22) is moved towards each other so that the point (22) of theknife (21) is inserted from behind at the exterior side of the rib head(13) of the rearmost rib (10 a) and the cutting edge (27) is brought toabut on a rib surface, and that the secured part carcass (2) and theknife (21) is moved further towards each other in the direction of thespine while the knife (21) is kept, seen along the cutting edge in thedirection of the point (22), in a predetermined angular positionobliquely inwards and upwards relative to the carcass (2), its centralplane and a second plane which is perpendicular to the central plane andin parallel with the spine (9) and the knife is moved along the ribsaway from the spine.
 2. A method according to claim 1, characterized inthat the point (22) of the knife at least during the first phase of thereleasing is moved substantially rectilinearly forwards relative to thepart carcass (2).
 3. A method according to claim 1, characterized inthat the position of the foremost rib (10 b) in the part carcass (2)relative to the knife (21) is detected, and that the movement of theknife (21) along the ribs away from the spine and the possible rotationof the knife around an axis parallel with the edge (22), depending onthe movement of the knife (21) and the part carcass (2) towards eachother in the direction of the spine, is controlled on basis of saiddetection.
 4. A method according to claim 1, in which the part carcass(2) comprises a sternum (11), characterized in that the knife, when theknife (21) has been advanced a distance along the ribs (10 a, 10 b) awayfrom the spine (9), is rotated about an axis which is substantiallyparallel to the cutting edge (27) into a smaller angle of attack withthe the ribs (10 a, 10 b), that the knife (21) during continued movementtowards the part carcass (2) in the direction of the spine is movedfurther away from the spine (9) obliquely towards the central plane ofthe carcass, and that the breast side, when the knife (21) has thus beenadvanced yet another predetermined distance is pressed downwards andtowards the carcass, following which the knife (21) under a continuousmovement relative to the part carcass (2) in the direction of the spineis taken sideways out from the part carcass.
 5. A method according toclaim 1, characterized in that the angle relative to the central planeis 15°-30°, preferably 20°-26°, and further preferably approximately 23°at least at the insertion of the knife (21) and when the knife (21)passes a possible sternum (11), and that the angle relative to thesecond plane is 5°-20°, preferably 7°-17° and further preferablyapproximately 11° at least at the insertion of the knife.
 6. A methodaccording to claim 1, characterized in that the cutting edge (27) iskept substantially at a constant angle relative to the central plane andthe second plane.
 7. A method according to claim 1, characterized inthat the knife (21) is pressed sideways against the ribs (10 a, 10 b)while moved along them and is rotated into a cutting angle adjusted suchthat the flank of the knife abuts the ribs (10 a, 10 b).
 8. A methodaccording to claim 1, characterized in that at the beginning the knife(21) is inserted at a predetermined spot relative to the holder (3, 4,5, 17) and next to the rearmost rib (10 a) at a distance therefrom, andis due to the insertion brought into abutment on this rib.
 9. A methodaccording to claim 1, characterized in that the knife is rotated aboutan axis containing the cutting edge (27).
 10. An apparatus for use inmechanical releasing of the ribs and the meat positioned therebetweenfrom the adjacent meat of a part carcass of a splitted carcass (2) witha spine (9), characterized in comprising a knife (21) having asubstantially rectilinear cutting edge (27) ending in a point (22) andbeing mounted in a knife holder (23, 24), a device with a holder (3, 4,5, 17) which can be brought into engagement with the part of the spine(9) of the part carcass carrying the ribs, and means (1, 4, 5) forestablishing a relative movement between the part carcass (2) and theknife (21) towards each other in the direction of the spine (9) andfurther to move the knife away from the spine.
 11. An apparatusaccording to claim 10, characterized in that the knife holder (23,24) isadapted to hold the knife with the cutting edge (27), viewed along thecutting edge in the direction of the point (22), at a predeterminedangle which, when the spine of a part carcass is in engagement with theholder, is obliquely inwards and upwards relative to the carcass (2),its central plane and a second plane which is perpendicular to thecentral plane and parallel with the spine (9).
 12. An apparatusaccording to claim 10, characterized in that the knife holder (23,24) isadapted to displace the knife (21) in a plane substantiallyperpendicular to the direction of the spine and preferably to rotate theknife about an axis which is parallel with the cutting edge (27).
 13. Anapparatus according to claim 10, characterized in a detecting device(37) for detecting the passage of the foremost rib (10 b) of a partcarcass (2) by a relative movement between a secured part carcass (2)and the knife (21) towards one another in the direction of the spine,and guiding means for guiding the displacement of the knife (21) awayfrom the spine and the possible rotation around an axis parallel withthe edge, depending on the movement of the knife and the part carcasstowards one another in the direction of the spine on basis of thedetection.
 14. An apparatus according to claim 10, characterized inshackles (39,40) for guiding the breast side of the part carcass (2).15. An asymmetric knife for use for mechanical cutting free of the ribsand the meat positioned therebetween from the adjacent meat in a partcarcass of a splitted carcass with spine, characterized in an elongaterigid blade (15) with a substantially rectilinear cutting edge (27)ending in a point (22), a bias cutoff of the blade (25) extending fromthe point (22), two substantially parallel side surfaces and a flank(26) angled relative to the adjacent side surface (30), said flankextending from the cutting edge (27) to a line positioned approximately4-25 mm, preferably approximately 5-20 mm, further preferablyapproximately 7-15 mm and for instance approximately 10 mm from thecutting edge, the angle (α) between the flank (26) and the adjacent sidesurface (30) being smaller than 180°, preferably smaller than 175° andfor instance approximately 170°.
 16. A knife according to claim 15,characterized in that the point (22) of the knife is bent out of theplane of the blade (25) opposite the side of the flank (26) and in thatpreferably a bevelling (28) is provided between the flank (26) and thecutting edge (27).